1. Field of the Invention
The present invention relates to an electronic device having a cooling system that cools a heat-generator such as electronic components like a CPU, and more particularly to an electronic device having a cooling system with improved cooling performance.
2. Description of the Related Art
Rapid headway is being made in making electronic devicesxe2x80x94in particular computers that contain CPUsxe2x80x94smaller in size and higher in performance. The electronic components such as CPUs built into such electronic devices generate heat during operation. If this heat is not radiated then the performance of the electronic components will drop and there will be a risk of them failing. A cooling system for the electronic components is thus necessary. As electronic devices have become smaller and thinner in recent years, the amount of space available in which to put a cooling system has decreased, meaning that high-performance cooling systems have become required.
FIGS. 10A, 10B and 10C illustrate conventional cooling systems used in electronic devices. FIGS. 10A, B and C show cross-sectional views of an electronic device, with a processor modulexe2x80x94on which is mounted a CPU (processor) and the likexe2x80x94and a memory which are built into the electronic device being shown as an example of a heat-generator.
First let us describe the positioning of the processor module 18 in the electronic device casing 10. In FIGS. 10A, 10B and 10C, a motherboard 12 is positioned on the bottom face of the electronic device, and a processor module board 16 is mounted on the motherboard 12 via a socket 14. A processor module 18 is mounted on the processor module board 16. A secondary cache memory 20 is also mounted on the processor module board 16. A thermally connecting material 22 is mounted on the secondary cache memory 20 in order to level the same with the processor module 18.
An example of a familiar cooling system for cooling a heat-generator such as the processor module 18 is a heat sink such as that shown in FIG. 10A. The heat sink has a base 24 and a heat-radiator 26. The base 24 has a face in contact with the heat-generator such as the processor module 18 and the memory, while the heat-radiator 26 comprises fins or the for expanding surface area so that heat can be radiated into the air efficiently. The base 24 and the heat-radiator 26 are, for example, formed integrally from a metal having a high thermal conductivity such as copper or aluminum.
As shown in FIG. 10A, the motherboard 12 is generally placed in the electronic device casing 10 in such a way that the face on which the processor module 18 is mounted is the upper face. This is because the processor module 18 is an electronic component that may need to be removed for maintenance or replacement, and is to facilitate such maintenance or replacement work. If the motherboard 12 is positioned in such a way that the face on which the processor module 18 is mounted faces downwards then the motherboard 12 itself would have to be removed from the electronic device in order to remove the processor module 18, making maintenance work less efficient.
When the processor module 18 is positioned in this way, the base 24 of the heat sink is in close contact with the upper face of the processor module 18xe2x80x94which is a heat-generatorxe2x80x94and thus absorbs heat from the processor module 18. If there is a space above the base 24 as shown in FIG. 10A, then the heat-radiator 26 is positioned in this space. The heat transported to the heat-radiator 26 is efficiently radiated by the current of air from a fan 28.
However, if for example as shown in FIG. 10B another electronic component 32 built into the electronic device such as a power supply unit or a channel card is positioned above the heat-generator, meaning that there is insufficient space above the processor module 18 in which to put the heat-radiator 26, then the base 24 is lengthened and the heat-radiator 26 is installed to the side of the processor module 18. In this case, in order to secure the volume required for the heat-radiator 26, the heat-radiator 26 can be in two portions, with one portion installed on the top of the base 24 and the other portion installed on the bottom of the base 24. This is because since the base 24 is positioned above the processor module 18, in the region to the side of the heat-generator there is a space below the extended part of the base 24 that goes from the motherboard 12 up to the height of the processor module 18.
FIG. 10B shows an example of securing the volume required for the heat-radiator 26. It shows that in the case that heat is transmitted through the heat sink by conduction, it is effective to install a portion of the heat-radiator 26 on the bottom of the base 24.
If the heat-radiator 26 of the cooling system is installed away from the heat-generator, then it is necessary to transport the heat absorbed by the base 24 to the heat-radiator 26 as efficiently as possible. Consequently, the base 24 may be a plate shaped heat pipe filled with a prescribed refrigerant that is more efficient at conducting heat than metal, or may have pipe-shaped heat pipes embedded in its metallic interior. Hollow parts for storing the refrigerant are provided inside the heat pipes, and heat is transported by the refrigerant vaporizing due to the heat and then migrating into the heat-radiator 26.
Moreover, in one known type of cooling system that uses a refrigerant, vaporized refrigerant circulates not only through the base 24 but also through the heat-radiator 26 (see for example Japanese Patent Application Laid-open No. 10-335552). With this type of cooling system, hollow parts for storing the refrigerant are provided in the base 24, and the heat-radiator 26 has a mechanism in which vaporized refrigerant flowing in from the base 24 is made to circulate and condenses.
In such a cooling system for which the refrigerant circulates through both the base 24 and the heat-radiator 26, the heat-radiator 26 must be installed on top of the base 24. Moreover, the region of the base 24 around where the heat-generator are installed must fundamentally speaking be immersed in the liquid refrigerant, or else there is a marked drop in performance. If the heat-radiator 26 is installed below the base 24, then the portion below the base 24 (on which the heat-generator are installed) becomes full of condensed liquid refrigerant, meaning that liquid refrigerant accumulates in the heat-radiator 26. In this case, vaporized refrigerant does not circulate through the heat-radiator 26 (which is full of liquid refrigerant) meaning that there is virtually no contribution to cooling.
With a cooling system in which the refrigerant flows into the heat-radiator 26, when the heat-radiator 26 is installed away from and to the side of the heat-generator, the heat-radiator 26 can thus only be installed on top of the base 24 as shown in FIG. 10C. However, with electronic devices being made smaller and thinner, there is a problem that there may not be sufficient height above the base 24, making it impossible to secure the volume required for the heat-radiator 26.
With the foregoing in view, it is an object of the present invention to provide an electronic device that contains a cooling system in which the refrigerant circulates through both the base and the heat-radiator, and the heat-radiator is installed away from and to the side of the heat-generator, and wherein it is possible to secure the volume (region) required for the heat-radiator.
In order to achieve the above-mentioned object, with the present invention, in an electronic device that contains a cooling system in which the refrigerant circulates through both the base and the heat-radiator and the heat-radiator is installed away from and to the side of the heat-generator, the heat-generator are positioned on top of the base. This means that the height of the base in the electronic device becomes relatively low,and so the height of the heat-radiatorxe2x80x94which must be installed above the height of the basexe2x80x94can be increased, meaning that the required heat-radiating region can be secured and high-performance cooling becomes possible.
An example of a configuration of the electronic device of the present invention for achieving the above-mentioned object is as follows:
An electronic device comprises
a heat-generator, and
a cooling unit including
a base having a first face that is thermally connected to the heat-generator and having a hollow part filled with a refrigerant inside, and
a heat-radiator that is thermally connected to the base and that has a space part that is linked to the hollow part,
wherein the heat-radiator is positioned above the base in the direction of gravity, and the refrigerant that vaporizes in the hollow part circulates through the heat-radiator and condenses to become a liquid,
wherein the heat-generator is positioned above the base in the direction of gravity.
In the above configuration, the heat-radiator is, for example, thermally connected to part of the first face of the base. Moreover, the base may have a projecting portion on the hollow part side of the first face in the region in which the base is thermally connected to the heat-generator, with this projecting portion extending into the hollow parts and being immersed in the refrigerant.